Metal surfaces that are coated with zinc-containing compositions or zinc alloy-containing compositions (e.g., GALFAN® and GALVALUME® alloy-coated steel sheets and strips) often exhibit better corrosion resistance than surfaces that are not coated with such compositions. Accordingly, galvanized (i.e., zinc-coated or zinc alloy-coated) surfaces are routinely utilized in a variety of industries, including the construction, vehicle, and appliance industries.
Even galvanized surfaces, however, are susceptible to corrosion over prolonged periods of time. Such corrosion, of course, comprises the integrity of products assembled with those products (particularly at bond lines), often rendering such products poorly suited or unsuitable for commercial use.
Moreover, it is well-known that it is difficult to bond galvanized surfaces together by means of conventional adhesives. Indeed, conventional adhesive compositions demonstrate poor adhesion to galvanized surfaces at room temperature. More significantly, when exposed to conditions of heat and humidity, conventional adhesive compositions exhibit minimal, if any, tensile strength.
Consequently, galvanized surfaces have traditionally been joined together by welding or mechanical fixing means (e.g., screws, rivets, and lock-forming means). Joining surfaces by welding or mechanical fixing means, however, is labor-intensive and expensive, and does not provide the advantages attendant use of adhesive compositions (e.g., weight-saving advantages, ease of preparation, and cost-effectiveness).
Thus, it would be desirable to provide compositions that (i) demonstrate improved bond strength on galvanized surfaces under various conditions, particularly under conditions of heat and humidity, and (ii) minimize and/or prevent corrosion on galvanized surfaces.